Also you can serve this with sliced chicken, salmon or shrimp.
Here is what you need to do:
In a saucepan, large enough to hold the fettuccine after you cook it, melt the butter over medium heat. Add in the cream and bring it to a simmer, not a boil. Whisk often for 5 minutes.
Add in the garlic, whisk for a minute. Add in the Parmesan and continue whisking until melted. Helpful hint the Parmesan will melt faster if it's a room temperature when you add it.
Add a little salt and pepper and taste. Adjust to your liking.
Cook the fettuccine according to package directions, minus about a minute because you are going to add it to your sauce where it will finish cooking. Also reserve a little pasta water to thin out the sauce if needed.
When the fettuccine is ready, add it to the sauce and toss to coat for about a minute. Slide into a serving dish and top with parsley and lemon if you like. Let's Eat!!